The present invention relates to windshield wipers for vehicles, and specifically to a drive mechanism for one or a pair of vehicle wipers of the type that overlap with respect to an inner wiping area.
Many vehicles include wipers that wipe back and forth simultaneously in the same direction using a tandem system. Some wiper systems operate simultaneously and in opposite directions, from a lowermost, inner wipe position to an outermost, outer wipe position and back. Wipers on large windshields are occasionally long enough so that the wipers overlap at the inner wipe area, with one wiper resting on top of the other wiper at the inner wipe position. In these situations, the drive mechanism includes a provision for preventing the top and bottom wiper from colliding as the lower wiper leaves the inner wipe position at the beginning of a wipe cycle, and as the wipers return to the inner wipe position at the end of the wipe cycle. Typically, a drive mechanism for such a system includes a bell crank linkage designed to begin moving the top wiper up from the inner wipe position faster than the bottom wiper at the beginning of the wipe cycle in order to prevent a collision between the wipers. The bell crank type of mechanism produces an undesirable result in that one of the wipers experiences sudden acceleration or whip at the outer wipe position, which can potentially take it past the ideal outer wipe position. This effect is particularly noticeable when the wipers are set at a high wiping speed.
The present invention relates to a windshield wiper mechanism including a pair of oscillated wiper blades having an overlapping wiping pattern at an inboard stroke end so as to substantially increase the wiped area of the windshield. The present invention provides a drive mechanism for oscillating the pair of overlapping wiper blades without interference. The drive mechanism imparts oscillation to a pair of spaced apart wiper blades from a rotary crank to obtain an overlapping wiping pattern adjacent the inboard stroke ends. The drive mechanism prevents collisions in the innerwipe position without causing high acceleration at the outerwipe position even at high speed wiper oscillation.
A windshield wiper drive according to the present invention imparts overlapping butterfly oscillation to a pair of spaced wiper shafts from a rotary drive member having a crank arm. A drive link is provided having first, second, and third connection points. The first connection point is adjacent one end of the drive link and pivotally connectable to the crank arm of the rotary drive member. The second connection point is adjacent an opposite end of the drive link. The third connection point is interposed between the first connection point and the second connection point along the drive link. An idler pivot link is pivotable about a fixed axis and has at least three crank arms extending radially from the fixed axis and spaced from one another. A first elongate link is pivotally connected at one end to a first crank arm of the idler pivot link and is pivotally connected at an opposite end to the second connection point of the drive link. A second elongate link is pivotally connected at one end to a second crank arm of the idler pivot link, and is pivotally connected at an opposite end to the third connection point of the drive link. The first and second elongate links cross with respect to one another between the idler link and the drive link. A third elongate link is pivotally connected at one end to a third crank arm of the idler pivot link and is pivotally connected at an opposite end for driving a first one of the pair of the spaced wiper shafts. Optionally, a fourth elongate link is pivotally connected at one end to a fourth crank arm of the idler pivot link, and is pivotally connected at an opposite end for driving a second one of the pair of spaced wiper shafts. Alternatively, a fourth elongate link can be pivotally connectable at one end to the crank arm of the rotary drive member and pivotally connectable at an opposite end for driving a second one of the pair of spaced wiper shafts.
In a windshield wiper drive system according to the present invention for imparting overlapping butterfly oscillation to a pair of spaced wiper shafts, an idler pivot link is connectable to at least one of the pair of spaced wiper shafts for imparting lower acceleration oscillation in proximity to a reversal position of each connected wiper shaft then the acceleration imparted intermediate a parked position and the reversal position of each connected wiper shaft. The idler pivot link is rotatable about a fixed axis and is connectable to at least one of the spaced wiper shafts for imparting a dwell in oscillation in proximity to a parked position of at least one of the connected wiper shafts.
Other objects, advantages and applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings.